#include<stdio.h>
void swap(int* x, int* y){
  int tmp=*x;
  *x=*y;
  *y=tmp;
  printf("in swap(): a=%d, b=%d\n", *x,*y);
}

int main(){
  int a=10, b=20;
  printf("a=%d, b=%d\n", a,b);
  swap(&a, &b);
  printf("a=%d, b=%d\n", a,b);
  return 0;
}
